Association of American Railroads (AAR) type E, type F and/or type E/F couplers are commonly employed in a railway car coupling systems. Type E couplers typically include a knuckle portion coupled to a tail portion via a transition portion. A hub pivotally couples the knuckle portion to a coupler head such that the tail pivots or rotates within a channel of the coupler head to engage a pulling surface to enable the coupler system of a leading railway car to pull a trailing railway car. The pulling surfaces of the tail and the coupler head are commonly referred to as pulling lugs.
In general, forming a knuckle to have a solid tail results in a heavy part that is also more likely to develop internal voids that can weaken or reduce the operating life of the knuckle. Thus, the cross-section of a tail of a knuckle typically has an open cored area to reduce the weight of the knuckle (i.e., lighten the knuckle) while providing acceptable internal solidity. The open cored area typically has a tubular or rectangular shaped cross-section. However, the tail may be susceptible to fatigue failure during operation because a relatively high stress is imparted to the tail when the knuckle is interlocked with a mating knuckle of another railway car. AAR standards and specifications (e.g., AAR specification M-211) indicates that the tail portion of a knuckle is a critical area and mandates periodic destructive testing of a used knuckle by cutting the tail portion to expose a cross-section of the tail that is inspected for factures, cracks and/or other damage.